• Transactions of Materials Processing
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• v.27 no.1
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• pp.18-27
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• 2018

As one of the functional metal parts in steam turbine diaphragm assembly, the hollow-partitioned turbine nozzle (stator) has large and thick geometries, as well as an asymmetric configuration. Therefore it is hard to support a metal blank in the die cavity. To ease this situation and control posture and position of metal blank (workpiece), a blank support structure is newly introduced. The blank support structure is basically composed of enlarged arms from the blank, guide pins and linear bearings. It can help to control the intermediate blank without a critical sliding phenomenon. The operation mechanism of this blank support structure, during thick plate forming for the hollow-partitioned turbine nozzle stator, is first evaluated. A series of FEM-based numerical simulations, with respect to the width of the guide arm as geometric design parameters, are carried out to investigate its applicable range. As the results, it is observed the blank support structure for this thick plate forming can guide the workpiece to have stable posture during the plate forming process.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.5
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• pp.29-36
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• 2014

The purpose of this study is to improve the Generic Agricultural Systems Simulator (GASS) which can simulate various rural systems based on object-oriented model. GASS provides the configuration platform of various system components to simplify integrated agricultural system models such as irrigation systems for rice farming. The new connection and communication modules of GASS improve applicability for modelling diverse systems. The geometric connection of GASS replaces topological connection, and communication protocols expand to analyze not only homogeneous system but also heterogeneous system. In this paper, we applied GASS2 to simulate the water heights of linked tanks and the simulation outputs were verified through comparing with analytical solutions of differential equations. The two new modules make it possible to analyze the 4-tank problem which includes topological and heterogenous issues with GASS2.

• Structural Engineering and Mechanics
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• v.54 no.3
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• pp.433-451
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• 2015

This paper focuses on large deflection static behavior of edge cracked simple supported beams subjected to a non-follower transversal point load at the midpoint of the beam by using the total Lagrangian Timoshenko beam element approximation. The cross section of the beam is circular. The cracked beam is modeled as an assembly of two sub-beams connected through a massless elastic rotational spring. It is known that large deflection problems are geometrically nonlinear problems. The considered highly nonlinear problem is solved considering full geometric non-linearity by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. There is no restriction on the magnitudes of deflections and rotations in contradistinction to von-Karman strain displacement relations of the beam. The beams considered in numerical examples are made of Aluminum. In the study, the effects of the location of crack and the depth of the crack on the non-linear static response of the beam are investigated in detail. The relationships between deflections, end rotational angles, end constraint forces, deflection configuration, Cauchy stresses of the edge-cracked beams and load rising are illustrated in detail in nonlinear case. Also, the difference between the geometrically linear and nonlinear analysis of edge-cracked beam is investigated in detail.

• Journal of Institute of Control, Robotics and Systems
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• v.8 no.2
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• pp.142-150
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• 2002

This paper presents a systematic method of the zigzag gait planning for quadruped walking robots. When a robot walks with a zigzag gait, its body is allowed to move from side to side, while the body movement is restricted along a moving direction in conventional continuous gaits. The zigzag movement of the body is effective to improve the gait stability margin. To plan a zigzag gait in a systematic way, the relationship between the center of gravity(COG) and the stability margin is firstly investigated. Then, new geometrical method is introduced to plan a sequence of the body movement which guarantees a maximum stability margin as well as monotonicity along a moving direction. Finally, an optimal swing-leg sequence is chosen for a given arbitrary configuration of the robot. To verify the proposed method, computer simulations have been performed for both cases of a periodic gait and a non-periodic gait.

• Journal of Korean Society of Steel Construction
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• v.23 no.2
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• pp.237-247
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• 2011

This paper presents an improved initial force method for determining the initial shape of suspension bridges. After determining the initial shape factors through the force equilibrium conditions of each hanging point, the initial force method was applied with the computed values, each node's coordinates, and unstrained lengths of the cable element as inputs. The unstrained length of each cable element was regarded as a fixed value in each iteration step, unlike in the typical initial force method. This method can be applied to 2D and 3D suspension bridge models. The validity of the present method was demonstrated by comparing the results of the numerical examples.

• Journal of the Korean Society of Propulsion Engineers
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• v.17 no.2
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• pp.84-93
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• 2013

Stealthy, high maneuverability and super cruise abilities are required for the next generation fighter and unmanned aircraft. Thrust vector control technique currently come into use to meet these requirements. In this experimental study, axial and pitch thrust were measured and Schlieren visualization were carried out using the scaled two dimensional thrust vector nozzles under various pitch deflection angle, pitch flap length and height. From the study, we could get the supersonic flow characteristics and draw an optimum geometric configuration of the two dimensional thrust vector nozzle.

• Journal of the Korean Solar Energy Society
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• v.35 no.1
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• pp.1-8
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• 2015

In the present study, the effects of the heat spreader thickness and the heat sink size on the thermal performance of a cooling device for a concentrating photovoltaic (CPV) module were numerically investigated. Numerical simulation was conducted by using the simulation tool ICEPAK, commercial software based on the finite volume method. Numerical results were validated by comparing the existing experimental data. The thermal performance of a cooling device, which consisted of a heat spreader and a natural convective heat sink, was evaluated with varying the heat spreader thickness and the heat sink size. The geometric configuration of the natural convective heat sink, such as the fin height, the fin spacing, and the fin thickness, was optimized by using the existing correlation. The numerical results showed that the thermal performance of the cooling device increased as the heat spreader thickness or the heat sink size increased. Also, it was found that the spreading thermal resistance plays an important role in the thermal performance of the cooling device which has the localized heat source.

• Wind and Structures
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• v.28 no.5
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• pp.331-345
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• 2019

Long-span bridge decks are often shaped as streamlined to improve the aerodynamic performance of the deck. There are a number of important shaping parameters for a streamlined bridge deck. Their effects on aerodynamics should be well understood for shaping the bridge deck efficiently and for facilitating the bridge deck design procedure. This study examined the effect of various shaping parameters such as the bottom plate slope, width ratio and side ratio on aerodynamic responses of single box streamlined bridge decks by employing unsteady RANS simulation. Steady state responses and flow field were analyzed in detail for wide range of bottom plate slopes, width and side ratios. Then for a particular deck shape Reynolds number effect was investigated by varying its value from $1.65{\times}10^4$ to $25{\times}10^4$. The aerodynamic response showed very high sensitivity to the considered shaping parameters and exhibited high aerodynamic performance for a particular combination of shaping parameters.

• International Journal of Internet, Broadcasting and Communication
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• v.11 no.2
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• pp.31-42
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• 2019

As smartphone H/W performance and mobile communication service have been enhanced, large-capacity 3D modeling files are available in smartphones. Common formats of 3D modeling files include STL (STereoLithography), OBJ (Wavefront file format specification), FBX (Filmbox), and glTF (open GL Transmission Format). Each format has different characteristics depending on the configuration and functions, and formats that are supported are varied depending on the applications. Large-size files are commonly used. The 4th generation mobile communication network secures loading of 3D modeling files and transmission of large-size geometric files in order to provide augmented reality services via smartphones. This paper explains the concepts and characteristics of major 3D file formats such as OBJ, FBX, and glTF. In addition, it compares their performance in a wired web with that in the 4th generation mobile communication network. The loading time and packet transmission in each 3D format are also measured by means of different mobile web browsers (Google Chrome and MS Edge). The experiment result shows that glTF demonstrated the most efficient performance while the loading time of OBJ was relatively excessive. Findings of this study can be utilized in selecting specific 3D file formats for rendering time reduction depending on the mobile web environments.

• Advances in Computational Design
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• v.4 no.2
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• pp.179-196
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• 2019

Temporary scaffold systems in the construction site play an important role for ensuring the safety of the workers and for constructing the stable structures. To assemble the scaffold, the pipe scaffolding system, the wedge binding scaffolding system and the particular materials have been utilized. To design the material arrangement of a scaffold, firstly the configuration was determined considering the construction geometry. Then, the strength of the scaffold was confirmed and the quantity of the material was accounted. In this paper, the design method of the temporary scaffold was proposed for intending the semi-automatic procedure. In the proposed design method, the geometric design and the safety requirement were specified by the safety standard and the design flow was followed by the designer's knowledge. The size and the quantities of the materials were calculated by referring to the relation between the scaffold and the constructing structure. In the calculating procedure, three dimensional positions of each scaffold materials were calculated and recorded simultaneously. Then, three dimensional scaffold structural was drawn semi-automatically on the CAD software by using the obtained material sizes, positions and directions. The proposed design method provides us the precise quantities of scaffold materials and enables us to reduce the design effort and the cost estimation processes. In addition, the obtained results can be applied to BIM software after converting to IFC format.